used on the RTF 2008 tour and you can see HERE!! This bass, as other's made for him have particular specifications as Mica said:

On Stan's personal basses the body is thicker at 1.79 inches and the accent laminates are also thicker at .25 inches. This is the same for the Vermilion bass you posted a link to and for the Coco Bolo bass you posted pictures of later.

Stanley's basses have one truss rod because the first ones he had only had one and he's very traditional. Notice his bass pickup is very close to the end of the fingerboard. Again, the first basses we made for him were done like this, and had no truss rod cover, so we still follow this tradition.

Another practical reason for a single truss rod in Stanley's basses is that his fingerboard dimensions are very narrow and the neck is carved very thin. A dual truss rod simply doesn't fit in this configuration.

We've never made Stan a spare set of hardware, so he's probably just using the original hardware. His tech will reintonate with different tunings.

Until 1998, we hadn't even made him a custom bass. He would order a standard short scale Series I, then have a repairperson local to him carve the neck smaller and sand away the finish off the back of the neck. When we made him the bass pictured above, he was happy to hear that he could open the case and have everything done just as he wished.

The bass pictured above was originally made with standard tuning. The near-matching Vermilion one was made originally with tenor tuning.

That is a string retainer bar. Normally on guitars and basses these are used where the tiltback angle of the headstock is shallow and these bars are used to create a sharp angle between the nut and the tuning pegs. It helps to keep the string tight in the nut and transfer more energy from the string into the neck. Typically you see them on Fenders which have little or no angle on the headstock and not on Gibsons where there is an angle.

Here are some examples I have found and hope they will help. A old example on an Orpheus Violin bass

Ibanez electric guitar

Another version by Wal bass

Here is one for sale on ebay. http://cgi.ebay.com/CHROME-4-String-Bass-STRING-Tree-RETAINER-BAR--Z94_W0QQitemZ140238027582QQcmdZViewItem